1. Field of the Invention
The present invention relates to an electroluminescent (the term “electroluminescent” will occasionally be referred to as “EL” hereinafter) element sealed by using a flexible film as a sealing base material.
2. Description of the Related Art
In recent years, Flat-Panel-Display (FPD) has increasingly been employed as a display which replaces CRT (Cathode-Ray-Tube) display which occupies a large space and has a relatively large weight. Examples of FPD include Liquid-Crystal-Display (LCD) which is widely and generally used as a display of various types of portable electronic appliances, a laptop-type personal computer and a small TV set. FPD of a type other than LCD, such as Plasma-Display-Panel (PDP), has also been generally employed.
Examples of FPD of a type other than LCD also include EL display. Although EL display has been studied for a relatively long timer EL display has not so widely been used due to problems of the difficulty in making EL display full-color and the relatively short product life.
Further, a film of an inorganic compound has conventionally been used as a luminescent layer of an EL element which constitutes EL display. However, an EL element using a film of an inorganic compound requires a relatively high driving voltage and exhibits a relatively low light-emission efficiency, thereby allowing only a display having low brilliance. On the other hand, in recent years, there has been used an EL element which employs, as a luminescent layer thereof, an film of an organic compound of which driving voltage is relatively low and light-emission efficiency is relatively high. In the case of an organic EL element using a film of an organic compound (an organic electroluminescent element), there has been a problem that the product life thereof is relatively short. However, as a result of the development of a material for an organic luminescent layer which enables prolonging the product life of an organic EL element, it is now possible to develop an organic EL element for practical use which can sufficiently compete with LCD.
Further, in recent years, there has increasing been a demand for an EL element having a thinner film, i.e., being more flexible. In order to meet such a demand, there has been proposed a method of using a flexible film as a sealing base material and laminating the sealing base material with a substrate under a predetermined pressure (the verb “laminate” will occasionally indicate this specific laminating process hereinafter”), thereby producing an EL element.
However, when an EL element is produced in such a laminating manner, as the strength of the organic EL layer is not so high, the organic EL layer is easily scratched or cracked by a slight impact or stress generated during the lamination process, whereby there arises a problem that the organic EL layer may fail to effect even luminescence.